Texan Guilty in Disputed Gun Probe

DALLAS—A member of a gun-smuggling ring linked to the shooting death of a U.S. immigration agent in Mexico pleaded guilty here Thursday to federal charges involving the illegal purchase of firearms.

The plea comes at a time when some Republicans in Congress are raising concerns that the agents in charge of the case in Texas might have intentionally allowed suspected smugglers to acquire guns, as other federal agents did in two operations in Arizona. In one Arizona sting, known as Fast and Furious, federal investigators...